Embodiments of the present invention relate to an apparatus and a method for detecting an array substrate.
At present, detecting apparatuses for a thin film transistor (TFT) array substrate in a liquid crystal display can be classified into two types: an electrical detecting apparatus type and an optical detecting apparatus type.
An electrical detecting apparatus may comprise a light source 102, a modulator 103 and a light receiver 105. As shown in FIG. 1, during the detecting process, an electric field is formed between a TFT array substrate 101 to be detected and the modulator 103 when electrical signals are applied to the pixels on the TFT array substrate 101. Light emitted from the light source 102 travels through the liquid crystal layer in the modulator 103 and then reaches a reflective thin film 104 on the modulator 103. At this time, the liquid crystal molecules in the liquid crystal layer in the modulator 103 are differently oriented based on the magnitude of the electric field formed therebelow. As the orientation angles of the liquid crystal molecules are varied, the amount of the light reflected back is varied. Then, the light receiver 105 (e.g., a camera) senses the reflected light and performs the analysis on sensed signals to determine whether a defect occurs based on the different intensity of the reflected light.
More specifically, the structure of the modulator 103 of the above-described electrical detecting apparatus for a TFT array substrate is shown in FIG. 2, and the modulator 103 comprises four layers: a transparent white glass layer 201, an ITO (indium tin oxide) conductive layer 202, a liquid crystal molecule layer 203 and a reflective thin film layer 204. The operating mechanism thereof is explained with reference to FIG. 3. In on example, when a voltage of 250V˜300V is applied to the ITO conductive layer 202 of the modulator 103 and a voltage of −18V˜30V is applied to the pixel electrodes on the TFT array substrate 101, an electric field is then generated between the modulator 103 and the TFT array substrate 101, and the liquid crystal molecules are oriented to align uniformly under the electric field to allow light to transmit. When testing signals are applied to the TFT array substrate 101, if a certain TFT device malfunctions, the intensity of the electric field formed thereabove may be decreased, and thus the orientation angles of the liquid crystal molecules may vary and the intensity of the light reflected back may be decreased.
An optical detecting apparatus is operated by irradiating light on a TFT array substrate, receiving light with a camera and the then analyzing the received signals. A defect pixel can be determined based on variation of the gray value of the light passing through the pixel compared with a normal value.
However, it has been found that there are at least following problems in the above conventional electrical detecting apparatus for a TFT array substrate. The electrical detecting apparatus determines a defect through sensing variation of the generated electric field, but some kinds of defects do not affect the electrical characteristics of a pixel but affect the aperture ratio of the pixel and thus cannot be detected by the electrical detecting apparatus. On the other hand, the optical detecting apparatus can only detect a surface defect of the pixel but cannot detect an electric defect. Therefore, two types of detecting apparatuses are needed to detect the kinds of defects of a TFT array substrate, resulting in a complex detecting procedure and a low detecting efficiency.